RU2265829C1 - Method of determining content of free furfurol in plywood sized with furan resin - Google Patents

Abstract

FIELD: woodworking industry.

SUBSTANCE: invention relates to a method for evaluation of toxicity sized wood products (plywood and wood chipboards) manufactured using furan resin. Method is accomplished by boiling plywood in ethyl alcohol for 3 h to promote free furfurol contained in plywood to pass into solution, wherein it is them measured by photocolorimeteric technique.

EFFECT: enabled evaluation of plywood toxicity.

1 dwg, 2 tbl

Description

The invention relates to the woodworking industry and can be used in the analysis of the toxicity of glued wood products (plywood and particle boards) made on the basis of furan resin.

A known method for determining the content of furfural in wastewater (Lurie Yu.Yu. Analytical chemistry of industrial wastewater. - M .: Chemistry, 1984, - 390 p., Vodzinsky Yu.V., Maslennikov A.S. Express methods for the determination of furfural. - M .: TsNIIIPI of the wood chemical industry, 1961, - 20 s).

This method is used to assess the content of free furfural in wastewater. It does not allow estimating the content of free furfural in glued plywood.

An object of the invention is to provide a method for evaluating the content of free furfural in glued plywood based on furan resin.

The task is achieved by boiling plywood in ethyl alcohol, as a result of which the free furfural contained in the plywood goes into a solution that is analyzed by the photocolorimetric method on a KFK instrument (cuvette photocolorimeter).

An essential feature that distinguishes the claimed technical solution from the prototype is that the plywood is boiled in ethanol for 3 hours, which is then analyzed by a photocolorimetric method on a KFK device.

An example of the method

In the presence of concentrated acetic acid, furfural is concentrated with aniline to form C ₄ H ₃ OCH (C ₆ H ₄ NH ₂ ) ₂ , which is intensely colored in red. Under these conditions, methylfurfural and hydroxymethylfurfural form yellow compounds, which practically do not affect the optical density of the solution, when measured with yellow-green filters. Oxalic acid, disubstituted sodium phosphate and sodium chloride are introduced into the analyzed solution to increase the stability of the resulting red color. The sensitivity of the determination is very high, at a wavelength of 518 nm, the molar absorption coefficient is 6.2 · 10 ⁴ .

The presence of free mineral acids in the analysis is unacceptable. With prolonged exposure to sunlight, the color is destroyed.

Reagents

Aniline is freshly distilled.

Glacial acetic acid.

Oxalic acid, 0.5% solution.

Sodium phosphate disubstituted, 10% solution.

Sodium chloride, 20% solution.

Ethanol.

A standard solution of furfural, which is prepared as follows. 3 g of freshly distilled furfural are dissolved in 1 l of distilled water, 1 ml of this solution is taken and diluted with distilled water to 100 ml. The resulting solution contains 30 μg furfural in 7 ml of solution.

Definition Progress

Into a calibrated 20 ml tube equipped with a ground stopper, 1 ml of freshly distilled aniline, 1 ml of glacial acetic acid, 2 ml of sodium chloride solution are introduced, mix thoroughly, 1 ml of oxalic acid solution, 1 ml of disubstituted sodium phosphate solution are added and the tube is placed on some time in a water bath with a temperature of 20 ° С, then 5 ml of the analyzed sample is poured into this test tube, ethyl alcohol is added to 20 ml, stirred and left in the dark in a water bath at a temperature of 20 ° С for 1 h.

The obtained colored solution is transferred to a cuvette with a layer thickness of 2 cm and the optical density of the solution is measured by the colorimetric method on a CPK device at a wavelength of transmitted light, possibly close to 518 nm. In the second cuvette, a solution of a blank experiment, carried out with 5 ml of ethanol and all reagents, is poured.

The furfural content in the analyzed solution is found according to the calibration schedule, for the construction of which 1, 2, 3, 4 and 5 ml of the standard furfural solution are taken, each portion is diluted with 5 ml of ethyl alcohol and the reagents are added to the mixture, as during the analysis of the sample.

Sample Preparation

The pressed plywood sheet is pressed after pressing to normalize the quality for 24 hours, then samples are cut out in a size of 10 × 20 mm for testing. Samples weighing 20 g are loaded into a round bottom flask with a ground stopper and reflux condenser, add 120 ml of ethyl alcohol, turn on heating and boil for several hours with sampling at regular intervals. An analysis of the results showed that the maximum amount of free furfural is released from plywood during the boiling period for 3 hours. The obtained alcoholic extracts are subjected to analysis in order to determine the amount of free furfural transferred from plywood to alcohol.

Results

The results of determining the optical density of solutions for constructing a calibration graph are presented in table. 1. The calibration graph is presented in the drawing.

To determine the free furfural content in plywood, a glued plywood sample was used, made on the basis of FA furfural acetone monomer, compressed according to the following regime:

- pressing temperature - 150 ° C;

- pressing pressure - 1.8 MPa;

- holding time without raising the pressure - 1 min;

- exposure time under pressure - 7.5 min;

- binder consumption - 110 g / m ²

The results of determining the content of free furfural in plywood are presented in table. 2. So the maximum content of furfural in plywood based on furan resin is observed after 3 hours of boiling in an ethyl sleep.

Table 1
The results of determining the optical density and concentration of solutions of samples of the calibration graph Calibration Graph Points Optical density Concentration of solutions
mg / l Measurement 1 Measurement 2 Measurement 3 Mean X1 0.879 0.880 0.881 0.880 0.86 X2 0,990 0,990 0,990 0,990 1.71 X3 0.157 1.18 1,158 1,158 2,57 X4 1,308 1,308 1,308 1,308 3.42 X5 1,414 1,414 1,414 1,414 4.28

table 2
The results of determining the content of free furfural in plywood Boiling time of samples, h Optical density Concentration according to the calibration graph, mg / l The content of furfural, mg / 100 g of plywood Measurement 1 Measurement 2 Measurement 3 Mean 1 0.899 0,900 0,900 0,900 1,03 1.77 2 1,160 1,160 1,161 1,161 2.61 4.99 3 1,210 1,210 1,211 1,210 2.88 4.96 4 1,199 1,199 1,199 1,199 2.73 4.70 5 1,195 1,195 1,196 1,195 2.68 4.62

Claims (1)

A method for determining the content of free furfural in glued plywood based on furan resin, characterized in that the plywood is boiled in ethanol for 3 hours, which is then analyzed by a photocolorimetric method on a KFK device.